Changes in char structure during the low-temperature pyrolysis in N2 and subsequent gasification in air of Loy Yang brown coal char

Abstract This study aims to investigate the changes in char structure during the pyrolysis in N 2 and subsequent gasification in air at low temperature in a thermogravimetric analyser. The chars produced from the gasification of Loy Yang brown coal in 15% H 2 O balanced with CO 2 at 850 °C in a fluidised-bed/fixed-bed reactor were used in this work. The evolution of char structure during pyrolysis and in-situ gasification was characterised by FT-Raman spectroscopy. The char-O 2 specific reactivity was measured as well. Our results show that, during further pyrolysis, the loss of O-containing structures led to the reduced observed Raman intensity from large aromatic rings and the formation of new cross-linking structures. During the subsequent gasification in air, the newly formed O-containing structures were more readily incorporated into less gasified char (0 min holding at 850 °C), but never reaching the same oxygenation level as those in the chars that had undergone extensive gasification (longer holding at 850 °C). The structural feature of the starting char (obtained at 850 °C) is the main factor determining the reaction pathway for the small/large aromatic ring systems during the low-temperature pyrolysis and in-situ gasification in air.